Over the last century astronomers have discovered a veritable zoo of strange objects inhabiting the Universe. Starting with other galaxies beyond our Milky Way they have also studied and named things like Pulsars and Quasars, Active Galactic Nuclei (AGN) and Black holes (see my posts of 17 April 2019 and 26 March 2022) and two distinct types of Supernova (see my posts of 26 May 2021 and 18 January 2020). Like any wildlife expert when astronomers find a new beast out there they first have to compare the object to a checklist of the things they already know before they even consider a new announcing a new species of astronomical animal. A case in point is the recent detection of a new radio source coming from a galaxy known as NGC 2082, a G type spiral about 60 million light years from the Milky Way with a diameter of an estimated 30,000 light years that lies in the constellation of Dorado in the southern hemisphere.
The emissions coming from NGC 2082 are currently being studied at radio frequencies by the Australian Square Kilometer Array Pathfinder (ASKAP), the Australian Telescope Compact Array (ATCA), the Parkes Radio Telescope along with visible light observations by the Hubble Space Telescope. What the Australians have found is a strong point source some 20 arcseconds from the center of NCG 2082 that has been given the designation J054149.24-61813.7. So far the observations of J054149.24-61813.7 tell us more about what the object isn’t that what it is. Looking at the chart below, which shows the spectral index of J054149.24-61813.7 it can be seen that the object’s power emissions as a function of frequency is pretty constant, unlike those a pulsar or supernova remnant.
In fact the flatness of J054149.24-61813.7 indicates that the radio emissions are thermal in nature, something like an AGN. However looking at the optical image above, taken by Hubble it can be seen that J054149.24-61813.7 is not at the center of NGC 2082 and in the close up lower left there does not appear to be any visual counterpart to the radio emissions. So, for the moment at least astronomers have a mystery on their hands and if further observations fail to find some clear link to a known type of radio source, perhaps a new species of object has been found for our astronomical zoo.
Not that we aren’t still discovering new details about the strange astronomical objects we already know about. Take neutron stars for example, those ultra dense objects who are the remnants leftover after supernova explosions, stars with the mass of our Sun crushed down to the size of a city. Neutron stars have gotten some press over the last few years because the first detection of gravity waves came from the merger of two neutron stars, see my posts of 17 April 2017 and 7 October 2017. Now a multi-disciplinary team of scientists have combined their observations and theories to produce a much more detailed model about the structure of neutron stars.
The study was led by theorists from the Technical University of Darmstadt in Germany and Utrecht University the Netherlands but it includes astronomical observations of neutron stars by radio and visible telescopes along with X-ray satellites. Also included were the results of heavy ion collision experiments conducted at Brookhaven National Labouratory in the US.
Those experiments were especially central to the modeling of neutron stars because, unlike the particle collision experiments performed in the Large Hadron Collider at CERN the collisions at Brookhaven are of entire gold nuclei being smashed together at velocities near that of the speed of light. That makes the conditions at Brookhaven much closer to the conditions inside a neutron star.
By combining the data from nuclear experiments here on Earth with observations of objects thousands if not millions of light years away the researchers hope to develop techniques for modeling many of the strange objects in the astronomical zoo. A multi-disciplinary approach combining astronomical data with the results of Earth bound experiments along with the latest theories, all in order to better understand our Universe.
Finally, in order to prove that the theoretical models they’ve developed are correct, astronomers have to compare the results of those models to observations of actual astronomical objects. That’s what astronomers at the University of Arizona are doing with the star VY Canis Majoris, a red supergiant that is considered to be the largest known star in the Milky Way.
Red giants like VY Canis Majoris have used up all the hydrogen fuel they initially possessed and are now using the helium produced by hydrogen fusion as their fuel. This change requires the core of the star to greatly heat up which causes the star’s outer atmosphere to expand, turning them into giants like Betelgeuse or Antares or VY Canis Majoris. In fact VY Canis Majoris has probably used up most of its helium fuel and may be getting very near the absolute end of its life.
Exactly how red supergiants end their lives is something of a controversial subject right now. It was thought that red giant stars exploded as supernova, leaving only a neutron star or back hole as a remnant but lately there has been evidence of the cores of some red supergiants simply collapsing into black holes without exploding. The astrophysicists at the University of Arizona hope to resolve some of this debate by comparing their models to VY Canis Majoris.
VY Canis Majoris is an excellent candidate for this study not only because it is simply the biggest star we know about but because, at a distance of 3,000 light years away it is also relatively nearby. That closeness will allow better, more detailed observations of the conditions on VY Canis Majoris to be made, enabling a more precise comparison to be made to the model. These are just a few of the techniques astronomers and astrophysicists use to study the many species of astronomical object that make up the cosmic zoo that is our Universe.